1. The Field of the Invention
This invention is in the field of instruments for use in medicine and dentistry. More specifically, this invention is in the field of endodontic irrigator tips for irrigating root canals as part of a root canal procedure.
2. The Relevant Technology
To preserve a tooth that has a diseased pulp cavity, it is necessary to prevent bacterial proliferation within the pulp canal of the tooth by removing the diseased or necrotic pulp material from the pulp canal. After the pulp material has been removed or extirpated from a tooth, the pulp cavity is typically filled or obturated with a material such as gutta percha to occlude the pulp cavity and a sealer to seal the pulp cavity. This procedure is referred to as root canal therapy. Root canal cleaning is generally achieved by hand or mechanical instrumentation with files that are configured to bore and cut.
It is also common during the root canal procedure to irrigate a pulp cavity and the various root canals involved using an endodontic irrigator tip. Irrigation assists in removing debris and necrotic material cut by the endodontic files and bores. Disinfecting solutions can also be employed in irrigation, thereby disinfecting the pulp cavity and root canals during the operative procedure.
In addition to being thin and tight, root canals are often twisted and cumbersome to negotiate. In order to place irrigator tips at a convenient angle within a tooth and negotiate the convoluted passages of root canals, irrigator tips are typically bent. U.S. Pat. No. 4,993,941 to Maita et al., for example, discloses a dental irrigator needle having a selectively angled cannula which was designed to provide more convenient fluid delivery.
The problem with this design, however, is that the needle itself is bent, which will potentially crimp a small, delicate root canal cannula. While it is possible to bend a larger diameter cannula without kinking or preventing the flow of the irrigation fluid therethrough, smaller diameter cannulas, which are particularly useful in tight root canal areas, are subject to crimping and breakage when bent. The problems associated with crimping of the cannula are particularly acute when thin, delicate irrigator tips are involved.
Another problem associated with root canal therapy is apical perforation. Before a file or irrigation tip is inserted into a root canal, the length of the root canal is determined to identify a suitable working length for the file or irrigation tip. Generally, the working length corresponds to the distance from a fixed reference position on the crown of a tooth to a location above the apical constriction of the root canal. Radiography is the most common method for measuring the length of the root canal. The preoperative x-ray image of the diseased tooth is taken from the front or back of the tooth as depicted in FIG. 1 to show a cross-sectional view of the root canals 12 of tooth 10. The length of the root canal and the desired working length of the cannula to be placed therein is then determined.
Perforation of the apex 14 of a root canal 12 can result from the use of files or endodontic irrigation tips which are too long. Such apical perforations typically result from an error in estimating the length of a root canal or the working length of the cannula Similarly, apex 14 can be perforated by extrusion of infected material through the apex due to the force exerted by the file or tip on the material as the file or tip is pushed downward to reach the apex. In addition to exposing the tissue surrounding the tooth to the infected material, apical perforations also substantially complicate subsequent healing of the root canal.
The possibility of perforating the apex is particularly frustrating because it is often desirable to deliver fluid which reaches the apex in order to disinfect the apex and dissolve necrotic tissue therein. However, certain fluids are too viscous to reach the apex if delivered too far above the apex. Sodium hypochlorite, for example, is a widely used, strong disinfectant that is viscous and can stick in the pulp chamber rather than reaching the apex if not delivered with precision from the appropriate location above the apex. Attempts to deliver the solution from the appropriate location, however, may result in the perforation of the apex.
Practitioners have made some attempts to place irrigator tips within teeth without perforating the apex. The working length of endodontic irrigator tips is sometimes limited by (i) bending the tips to prevent them from extending too far into a root canal, or (ii) marking the tips with a pen at a location on the tips which should not extend past the rim of the crown. The problem with each of these approaches, however, is that they are unreliable, and can contaminate the tip as a result of the handling of the tip prior to use. In addition, bending a cannula can crimp or kink the cannula.
The possibility of perforating the apex of the root canal with an endodontic file is sometimes prevented by employing a removable stop which is placed about the distal insertion end of the file and pushed a desired distance toward the proximal gripping end of the file. Such adjustable stops, however, are prone to slip and slide along the longitudinal axis of the file, thereby allowing perforation of the apex. In addition, placing a stop on the file requires handling of the file prior to use, possibly contaminating the file.
Irrigating probes used for other dental applications also fail to solve the problems associated with typical endodontic irrigation probes. For example, U.S. Pat. No. 5,127,831 to Bab discloses a flexible end irrigation probe which is designed for irrigating periodontal pockets. The design features an irrigator having a smooth transition between a flexible plastic distal end and a more rigid arm which extends from the hub. This smooth transition is important to the design because the irrigator is configured to achieve atraumatic nonsensitizing penetration into periodontal pockets. The Bab device would not be desirable for root canal therapy because the smooth transition of the Bab irrigation probe fails to provide a stopping mechanism which would prevent the irrigator from extending beyond a desired distance.
Another problem associated with the cannulas of typical endodontic irrigator tips is that it is sometimes desirable to be able to gently press the tip of a cannula through tissue in order to reach the area in which irrigation is desired. Typical orifices, however, are subject to being clogged by the tissue during this process. Furthermore, typical orifices can sometimes spray the irrigating fluid with too great of force directly into a particular location. Finally, certain cannulas are too obtrusive to root canal surfaces or are inefficient to manufacture.
There is therefore a need within the art for an endodontic irrigator tip having a cannula that can be conveniently used without crimping and without risk of apical perforation. There is also a need within the art for different irrigator tips which can be used to buffer the impact of liquid delivered into a root canal, extend a cannula through a tissue in order to reach a desired irrigating area, prevent the manipulation of root canal surfaces, or are efficient to manufacture.